1. Field of the Invention
The present invention relates to projectors for displaying images through projecting light onto a screen, and, in particular, relates to technologies for keystone correction for correcting trapezoidal distortion of images on a screen.
2. Description of the Related Art
When displaying images on a screen using a projector, there may be trapezoidal distortion of the image that is displayed on the screen (hereinafter termed the “displayed image”) given the relative positioning of the projector and the screen. There are known technologies for keystone correction by which to correct the trapezoidal distortion of the displayed image in such a case.
For example, in keystone correction, an image of the screen is captured using an image capturing device, such as a CCD, the frame (outside perimeter lines) of the screen is detected using the captured image, and, based on the shape of the frame of screen that has been detected, the image on the liquid crystal panel in the projector is formed through compression into a trapezoidal shape. (See, for example, JP2002-62842A and JP2002-247614A).
However, in the conventional technologies described above, it is necessary to detect all four of the edges of the screen frame in the captured image. The reason for this is that when the four edges of the screen frame are detected, it is possible to calculate the shape of the screen using each of the edges that have been detected. Consequently, conventionally, there has not been a known technology for keystone correction that takes into account cases wherein only three or less of the edges of the screen frame are detected.